Sealing method and apparatus

ABSTRACT

A high-dwell, high pressure, and low temperature method and apparatus for sealing heat sealable flexible containers. The flexible containers are sealed before moving out of a sterilizing chamber maintained at a sterilizing temperature of between about 212* and 250* F. Sealing bars are heated to a temperature of between about 250* and 300* F., and are clamped against the container at a pressure above 100 p.s.i., preferably about 250 p.s.i. for a period of between 2 to 6 seconds, preferably about 4 seconds.

United States Patent Wilson [451 Mar. 21, 1972 54 SEALING METHOD ANDAPPARATUS 3,182,432 5/1965 Canfield 53/373 x 3,230,687 1/1966 Nutting etal.. ..53/28 X [72] Inventor. Donald C. Wilson, San Jose, Calif.3,430,414 M1969 Ludwig et al 53/112 8 X [73] Assignee: FMC Corporation,San Jose, Calif. 3,488,914 1/1970 Csemak ..53/373 X [22] Filed: Sept1969 Primary ExaminerRobert L. Spruill 2 Appl. 860,335 Attorney-F. W.Anderson and C. E. Tripp [57] ABSTRACT [52] US. Cl ..53/l27, 53/89,53/167, v

' 5 3 /373 156/381 A high-dwell, high pressure, and low temperaturemethod and 51 Int. Cl. ..B65b 7/06 B6515 55/06 alPParatus Sealing heatscalable flexible The 58 Field of Search 53/86, 89, 1 12 3, 127, 167,flexible mainers are Sealed befm Wing sterilizing 53 373; 156 381 382,494, 538 chamber maintained at a sterilizing temperature of between Iabout 212 and 250 F. Sealing bars are heated to a tempera- [56]References Cited ture of between about 250 and 300 F., and are clampedagainst the container at a pressure above 100 p.s.i., preferably UNITEDSTATES PATENTS about 250 p.s.i. for a period of between 2 to 6 seconds,

preferably about 4 seconds. 2,277,288 3/1942 Berch ..53/373 X 2,441,9405/1948 Rohdin ..53/373 X 11 Claims, 17 Drawing Figures SEALER AT 280' F2l2F STEAM 7A u 3 l o a 58 3 SS STERILIZER PAIENTEDMAR21 I972 3550.088

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T I E 2 I DONALD 0. WILSON BYjw ATTORNEYS PATENTEDMAR21 m2 3,650,088

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PATENTEUmenerz 3.650088 SHEET sum 10 PAIENTEUMAR21 m2 SHEET USUF1OPATENTEDMARZI I972 SHEET O7UF 10 PAIENTEBMARm m2 SHEET UBUF 1O OWN wmN

UH F H-HIF PATENTEDMARZI I972 SHEET IUUF 10 LS1 LS2 286 548 I CROSSREFERENCE TO RELATED APPLICATIONS The sealing method and apparatus ofthe present invention may be used in the type of apparatus disclosed inmy copending application Ser. Nos. 693,330 and 772,321, whichapplications issued as US. Pat. Nos. 3,501,318 and 3,528,826,respectively, and are assigned to the assignee of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention pertains to the art of sealing containers which includeabutting surfaces of thermoplastic materials which are sealed togetherby application of heat and pressure, and more particularly relates to ahigh-dwell, high pressure and low temperature method of sealingthermoplastic flexible containers or pouches.

2. Description of Prior Art Heat sealable containers such as flexiblecontainers, also referred to as pouches, having sealing surfaces ofthermoplastic material are usually sealed when at or below roomtemperature by sealing bars which subject the container walls to a hightemperature of between about 450 to 600 F. at a low pressure of about 40p.s.i. and for a short time of about 0.5 second or less. When sealingflexible pouches in accordance with this conventional method, the hightemperatures necessarily require low pressures to prevent excessive flowof sealing material. The low sealing pressure is usually inadequate toremove contamination, such as food particles, from the 'area beingsealed, which contamination absorbs the sealing heat from the sealingmaterial thus resulting in a poor seal. It is also recognized that hightemperatures may, under certain conditions cause undesirable chemicalreactions to take place with the materials of the laminated pouch.

SUMMARY OF THE INVENTION In accordance with the sealing method andapparatus of the present invention the containers are sealed while inthe sterilizing chamber immediately before the hot containers areconveyed out of the sterilizing chamber. If the sterilizer is anatmospheric sterilizer the entire container and food product therein isheated to about 212 F. and the sealing bars are heated to about 280 F.thus requiring that only about 68 F. be added to the container sealingsurfaces to heat these surfaces to the desired sealing temperaturewithin a period of about 4 seconds when subjected to a sealing pressureof about 200 p.s.i. Similarly, when the sterilizer is a superatmosphericsterilizer and the sterilizing temperature is 250 F., sealing bars whichare heated to about 280 F. and are subjected to about 200 p.s.i. for aperiod of 4 seconds would raise the temperature of the sealing surfacesufficient to hermetically seal the container. Under these conditions itis noted that the sealing bars need be heated only about 30 F. higherthan the sterilizing temperature.

It has been discovered that the contamination problem is greatly reducedwhen sealing flexible containers in accordance with the presentinvention. Since the containers and food particles are at thesterilizing temperature immediately prior to the engagement of thecontainerwalls by the sealing bars, any food particles remaining in thesealing area are at the sterilizing temperature and accordingly aresoftened and do not draw excessive amounts of heat from the sealant inthe sealing area. Since the low temperature permits the use of highsealing pressures without danger of extruding the sealant from the sealarea, this high sealing pressure extrudes the contaminates from thesealing area before the temperature of the sealant has reached thesealing temperature.

Because of the long dwell during sealing and because the containers aremoving continuously during sealing, the sealing apparatus of the presentinvention is arranged to reciprocate with the containers so as to moveat the same speed and in the same direction as the containers during thesealing operation and move in an opposite direction when returning toengage and seal the next following container.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic centralvertical section of an atmospheric cooker and cooler within which thecontainer sealing apparatus of the present invention is positioned.

FIG. 2 is a diagrammatic central vertical section of a high pressurecooker and cooler within which the container sealing apparatus of thepresent invention is positioned.

FIG. 3 is an enlarged vertical section taken along lines 3-3 of FIG. 1illustrating the sealing bars associated with a tworow atmosphericsterilizer, one sealing bar being removed so as to more clearlyillustrate the linkages.

FIG. 4 is a perspective view of one of the sealing heads showing thehead in an open position ready to engage a flexible container supportedin a carrier, a pneumatic power unit being removed to better illustratethe linkages of the sealing head.

FIG. 4A is a side elevation of the sealing head of FIG. 4 shown insealing engagement with a flexible container immediately prior to thecompletion of the sealing operation.

FIG. 4B is an enlarged section showing a locking finger engaged with thecontainer transport conveyor.

FIG. 5 is a diagrammatic operational view illustrating one of thesealing heads in a retracted open position disengaged from the conveyor,the container clamps of the carrier being omitted for clarity.

FIG. 6 is an operational view similar to FIG. 5 illustrating the sealinghead in a retracted open position but engaged with the conveyor andaligned with a flexible container to be sealed.

FIG. 7 is an operational view similar to FIG. 5 illustrating the sealinghead in an active sealing position near the end of its sealingoperation.

FIG. 8 is a diagrammatic pneumatic and electrical diagram illustratingthe control circuit for the first embodiment of the invention.

FIG. 8A is a diagrammatic vertical section taken through a speed controlvalve.

FIG. 9 is an enlarged horizontal section taken substantially along lines99 of FIG. 2 illustrating a second embodiment of the sealing head of thepresent invention, certain parts being cut away.

FIG. 10 is a vertical section taken substantially along lines 10-10 ofFIG. 9, one sealing bar being removed so as to more clearly illustratethe linkages.

FIG. 11 is an operational view illustrating the sealing head in aninactive rearward position.

FIG. 12 is an operational view similar to FIG. 10 but illustrating thesealing head in a forward sealing position and in engagement with theconveyor.

FIG. 13 is a perspective view of one of the carriers associated with thesecond embodiment of the invention.

FIG. 14 is a diagrammatic pneumatic and electrical diagram illustratingthe control circuit for the'second embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENT The sealing head 20 (FIGS. 3 to 7)of the first embodiment of the invention or the sealing head 22 (FIGS. 8to 11) of the second embodiment of the invention may be placed either inan atmospheric cooker and cooler 24 (FIG. 1) at a sealing station SS ormay be employed in a superatrnospheric cooker and cooler 26 (FIG. 2) ata sealing station SS. Since the sealing heads of either the first orsecond embodiment of the invention may be used with either theatmospheric cooker and cooler 24 or with the superatmospheric cooker andcooler 26, the cookers and coolers will first be briefly described andthereafter the two embodiments of the sealing heads will be described.

The atmospheric cooker and cooler 24 (FIG. 1) comprises a housing whichdefines a sterilizing chamber 31 having vertical side walls 32 (only onebeing shown in FIG. 1), a floor 34, a roof 36, a first end wall 38having a downwardly inclined inlet tunnel 40 therein, and a second endwall 42 having a downwardly inclined discharge tunnel 44 therein. Anendless conveyor 46 is trained along a vertical zigzag path through thehousing 30 by upper sprockets 48 and lower sprockets 50 secured toshafts 52 journaled in the side walls 32. The conveyor 46 is alsotrained around outer sprockets 54 which guide a return run of theconveyor over the housing 30 and over a cooling trough 56. The conveyoris driven by motor 58 and a chain drive 60 that is connected to one ofthe shafts 52.

The conveyor 46 advances rows of flexible containers C through thesterilizing chamber along a zigzag path so that the containersalternately dip into water in the lower portion of the housing, whichwater is heated to about 212 F. by steam from a conduit 62, and throughsteam at about 212 F. in the upper portion of the housing. As describedin my aforementioned copending applications, when each container issupported so as to provide a one-way valve in its open end, thealternate movement through steam and hot water in the sterilizingchamber 31 causes air and cooking gases to be purged from the containerand also sterilizes the food product within the containers. Thesterilized containers are then moved into the sealing section SS in theupper portion of the sterilizing chamber 31 and are sealed while at thesterilizing temperature either by the sealing head of the firstembodiment of the invention or the head of the second embodiment of theinvention. The containers are then cooled as they pass under cold watersprays emitted from a cooling conduit 64 and are subsequently removedfrom the conveyor and are replaced by other filled containers to besterilized.

The superatmospheric cooker and cooler 26 (FIG. 2) is in the form of ahydrostatic cooker. The cooker and cooler 26 includes a housing 66 whichcomprises a pair of spaced vertical support walls 68 (only one wallbeing shown in FIG. 2) that are supported in spaced parallelrelationship. A sterilizing housing 70 that extends between the twowalls 68 has a roof 72 and two depending walls 73 and 74 which cooperatewith the two walls 68 to define a cooking or sterilizing chamber 76which is filled with steam at a predetermined cooking pressure andtemperature, for example, at about 250 F. and 15 p.s.i gauge. The lowerend of the housing 70 opens into a water filled trough 78 which isformed by the two walls 68, a transverse horizontal floor plate 80 andthe lower end portions of two transverse vertical walls 82 and 84. Thewall 82 cooperates with another transverse vertical wall 86 to define aninlet hydrostatic water leg 88, and a wall 84 cooperates with atransverse vertical wall 90 to provide an outlet hydrostatic leg 92. Thehydrostatic legs 88 and 92 communicate with the trough 78 and are filledwith water from conduits 94 so as to create sufficient pressure toresist the pressure of steam in the sterilizing chamber 76. Steam isdirected into the sterilizing chamber 76 through a manifold 96 and avalved conduit 98.

The inlet hydrostatic leg 88 is thermostatically controlled to provide atemperature of about 210 F. from the upper end to the lower end of theleg 88. The outlet water leg 92 is also thermostatically controlled andhas cooling water added thereto to provide a decreasing watertemperature which cools the contents of the containers to a temperaturebelow the boiling point of water at atmospheric pressure. Steam is addedto the water in the hydrostatic inlet leg to provide the desired heatingtemperature therein, and cooling water as mentioned above is directedinto the cooling leg 92 to provide the desired cooling temperaturetherein.

A processing conveyor 100 is trained around a plurality of sprockets 102and associated guide tracks (not shown in FIG. 2) and is driven by amotor 104 and chain drives 106, 108 and 110 so as to move the conveyordownwardly into the inlet hydrostatic leg 88, through a vertical zigzagpath in the sterilizing chamber 76, past the sealing station SS in thesterilizing chamber at which time the containers are sealed, through theoutlet leg 92, and back to the inlet leg 88.

For convenience of description, the sealing head 20 of the firstembodiment of the invention will be described in con- 5 junction withthe atmospheric cooker and cooler 24, and the sealing head 22 of thesecond embodiment of the invention will be described in conjunction withthe superatmospheric cooker and cooler 26.

The sealing method and apparatus of the present invention has beenoperated successfully to seal the following types of triple layerlaminated pouches:

POUCI-IES 5' X 7" It will also be understood that the sealing method andapparatus is operable with other types of laminated materials, andfurther be understood that the sealing temperature increases as thethickness of the inner layer increases. If aluminum foil is not presentin the laminated pouch, the sealing temperature is lowered.

The sealing head or apparatus 20 (FIGS. 3 to 7) is designed to handletwo rows of containers C with the rows being disposed on opposite sidesof a single endless hollow pin chain of the conveyor 46. The chain 120has a plurality of carrier supporting rods 122 pivotally supportedthereon at spaced intervals therealong, which rods project equaldistance outwardly from both sides of the chain. A carrier 124 issupported on each end of the rod 122, and the carrier is held in placeby a locknut 126 and cooperating spacers 127 between the chain 46 androd 122. As best shown in FIG. 4, each carrier includes side walls 128which are formed into a generally V-shaped pocket 130 within which acontainer C is manually placed. An inner wall 132 is pivotally connectedto one end of the associated rod 122 as above described at a pointslightly above the side walls 128 and extends upwardly from the pivotpoint to a position adjacent the upper end of the container. A springloaded clamp 134 is secured to the upper end of the inner wall 132 andis clamped to one edge of the container. A leaf spring 136 is bolted tothe outer wall 138 of each carrier 124 and has a clamp 140 secured toits upper end. The clamps 134 and 140 are secured to opposite edges ofthe flexible container near its upper end and the leaf spring 136 urgesthe clamp 140 away from the clamp 134 to apply a tensioning force acrossthe mouth of the container. As described in detail in my aforementionedcopending applications, this tensioning force forms a one-way valve inthe mouth of the container thereby allowing air and cooking gases to bepurged from the container preventing flow of gases or liquids into thecontainer.

Two sealing heads 20a and 20b (FIG. 3), one for each row of containers,are provided and each head includes a pair of spaced support arms and152 which are rigidly secured to a shaft 154 that is journaled in theside walls 32 of the housing 30 at the sealing station SS. Since the twoheads are identical only one head will be described in detail.

The head 20a (FIGS. 3 to 7) includes the spaced arms 150 and 152 whichhave a pivot shaft 155 secured to their lower ends. A front sealing bar156 is secured to two lever arms 158 and 160 that are joumaled on theshaft 155 and extend upwardly therefrom. Similarly, a rear sealing bar162 is secured to two lever arms 164 and 166 that are joumaled on theshaft 155 and extend upwardly therefrom.

The upper ends of levers 158 and 160 are connected by a shaft 168 whichextends through horizontal slots 170 into spaced cam plates 172 thatform a part of a vertically reciprocable carriage 174. The upper ends ofthe levers 164 and 166 likewise are connected together by a shaft 176which extends through horizontal slots 178 in the two cam plates 172. Itwill be apparent that as the front sealing bar 156 and rear sealing bar162 pivot about the shaft 155 from the open or inactive position shownin FIG. 6 to the sealing position shown in FIG. 7, the engagementbetween the shafts 168 and 176 and their associated slots 170 and 178will cause the carriage to lower.

As best shown in FIGS. 4 and 4A, the carriage 174 includes the camplates 172 which are welded to angle bars 180 that are in turn welded totwo horizontal slide plates 182 that slidably engage the narrow edges ofthe spaced support arm 150 and 152. The carriage 174 also includes slideplates 184 that are welded to the associated angle bars 180 and slidablyengage the inner flat surfaces of the support arms 150 and 152 andcooperate with the plates 182 to guide the carriage along a pathparallel to the arms 150 and 152 during its reciprocable movement.

A power unit which is illustrated in the drawings as a pneumatic ram 186is provided to move the sealing bars 156 and 162 between their inactiveand sealing positions. As best shown in FIGS. 5 to 7, the cylinder 188of the ram 186 is rigidly secured as by welding to the shaft 176 whileits piston rod 190 is pivotally connected to the shaft 168. Since thecarriage 174 is guided so as to move only in a direction parallel to thearms 150 and 152, it will be apparent that engagement between the slots170 and 178 and shaft 168 and 176 will cause the sealing bars 156 and162 to move equal amounts in opposite directions upon actuation of thepneumatic ram 186.

Since the dwell period during which the sealing jaws are clamped againstthe container walls is relatively long, i.e., between about 2 to 6seconds, it is apparent that the jaws must move with the containerduring the dwell period. In order to move the head with the containers,the cylinder 192 of a pneumatic ram 194 (FIG. 3) is rigidly secured to atab 196 that is welded to the arm 150. A chain engaging finger 198 isscrewed into the piston rod 200 of the ram 194 and is locked in desiredposition by locknut 202. As best shown in FIG. 5, the lower end of thefinger 198 is shaped so as to fit between adjacent pivot pins of theconveyor chain 120 thereby operatively con necting the lower portion ofthe head to the chain 120 causing the sealing head 20 to pivot about theaxis of the shaft 154.

The finger 198 when in its lower chain engaging position causes thechain to bow downwardly a small amount as shown in FIGS. 6 and 7 therebyassuring that the chain will remain in tight engagement with the finger198 during the entire sealing operation and further assuring that therewill be no tendency for the jaws to attempt to lift the container fromits carrier because of the arcuate movement of the sealing head 20. Itwill also be appreciated that the upper portion of the container issomewhat flexible and that the carriers are pivoted to the conveyorchain so that the container and carrier may freely pivot or deflectslightly and remain in substantially radial alignment with the arcuatepath of movement of the sealing head 20 during the sealing operation.

A pneumatic and electrical circuit 206 (FIG. 8) is provided to actuatethe closing of head 20a in timed relation with the movement of theconveyor 46. As diagrammatically indicated in FIG. 8, air is receivedfrom a source of high pressure air and is directed through pressureregulator PR. A conduit HP is connected to a solenoid operated valve208, and low pressure air is vented through conduit V. The pressureregulator PR is of the well known adjustable type which may be adjustedso as to provide a sealing pressure above p.s.i., preferably about 250psi. The valve 208 includes a shiftable core 210 which, when thesolenoid 212 is energized, aligns parallel passages 214 and 216 with theconduits V and HP, respectively, and also with conduits 218 and 220respectively. When the solenoid is deenergized a spring 221 moves thecore to a cross passage position.

Conduit 220 communicates with the upper end of the cylinder 192 and hasa speed control valve SC (FIGS. 8 and 8A) therein. Conduit 220 alsocommunicates with the upper end of the sealing cylinder 188 of a ram 186through conduit 222 and another speed control valve SC. Conduit 218 isconnected directly to the lower end of the cylinder 188 and is alsoconnected to the lower end of the cylinder 192 through conduit 224 whichhas a speed control valve SC therein.

Each speed control valve SC is oriented as indicated in FIG. 8A so thatdownward movement of fluid will urge a ball 226 into sealed engagementwith a valve port 228 in a main passage 230 thereby causing the fluid toflow through a branch passage 232. A needle valve 234 is provided in thebranch passage and may be adjusted to vary the rate of fluid flowtherepast. Flow of fluid in the opposite direction, i.e., upwardly asviewed in FIGS. 8 and 8A, will raise the ball 226 from its valve port228 thus allowing substantially unrestricted free flow of fluidtherepast.

As diagrammatically illustrated in FIG. 8, the solenoid 212 of the valve208 is energized by closing a normally open switch S1 by one of thecarrier supporting rods 122 when a carrier is moved into position to besealed. The switch S1 includes an elongated actuating element 238 whichis actuated by the carrier supporting rod 122. The switch S1 isconnected in series between main lines L1 and L2 with a relay A of atimer or time delay relay and a closed timer contact TC. Momentaryclosing of switch S1 energizes the relay A through the closed timercontact TC. Energization of the timer relay A closes relay contact A-1forming a holding circuit across the switch S1 and also closes relaycontact A-2 which closes a circuit to the solenoid 212 of the valve 208thereby shifting the core 210 to the straight passage position shown inFIG. 8. High pressure air is then directed through lines 220 and 222 tothe upper ends of the cylinders 192 and 188 of the rams 194 and 186. Thespeed control valves SC are regulated so that the ram 194 is actuatedprior to actuation of the ram 186 so that the sealing head 20 will beconnected to the conveyor chain 122 prior to movement of the sealingbars 156 and 162 into engagement with the container being sealed.

The valve 208 remains in the position described immediately above untilthe dwell period set on the timer, i.e., between 2 to 6 seconds, elapsesat which time the timer contact TC momentarily opens to deenergize thetimer relay A thereby opening contacts A-1 and A-2 and deenergizingsolenoid 212 returning the core 210 of the valve 208 to thecross-passage position. High pressure air is then directed through lines218 and 224 to the bottom ends of cylinder 188 and 192 of the rams 186and 194. The speed control valve SC resists flow of fluid into the ram194 thereby permitting the sealing bars 156 and 162 to release thecontainer C before the finger 198 is raised from engagement with theconveyor chain 120.

The sealing apparatus 22 (FIGS. 9 to 14) of the second embodiment of theinvention will be described in conjunction with the superatrnosphericcooker and cooler 26 illustrated in FIG. 2. It is to be understoodhowever that the sealing apparatus 22 may also be used with anatmospheric cooker and cooler of the type disclosed in FIG. 1.

The sealing apparatus 22 as illustrated is associated with a two-rowcooker and cooler 26 and includes a sealing head 23 for each row. Theprocessing conveyor 100 includes two spaced endless chains 250 guidedthrough the sealing section SS by tracks 252 interconnected by aplurality of evenly spaced rigid U-shaped double carriers 253 (FIG. 13)that are pivotally connected to the chains 250. The double carriers 253include four upstanding spring loaded arms 254 which have spring clips255 on their upper ends that grip the side edges of the flexiblecontainers C to apply a tensioning force across the mouth of eachcontainer to define a one-way valve therein. The carriers also includespring clips 256 which engage the lowered ends of the containers andprevent flotation of the flexible containers as they are being movedthrough liquid heat treatment mediums within the cooker and cooler 26.

The sealing apparatus 22 comprises a frame 258 having longitudinalmembers 260 which are rigidly secured to the side walls 68 of thehousing 66 near the discharge end of the sterilizing chamber. Twotransverse frame members 262 (only one being shown in FIGS. 9 to 12)support a pair of elongated guide rods 264. As best shown in FIGS. 11and 12, the guide rods 264 slidably support a carriage 266 by means ofcollars 268 that are secured to a sub-frame 270. The sub-frame carriesthree power units which are illustrated as pneumatic rams; and indexingram 272, a sealing ram 274, and a carriage return ram 276.

The indexing ram 272 includes a cylinder 278 that is pivotally mountedon the sub-frame 270 and has its piston rod 280 pivotally connected to alever 282 that is keyed to a cross shaft 284 pivotally supported by thesub-frame 270. A pair of spaced hooking arms 286 are keyed to the shaft284 and are movable by the indexing ram 272 between an upper inactiveposition as shown in FIG. 11 and a lower active position illustrated inFIG. 12. As will be described later, the piston rod is moved to itsretracted position when the conveyor has moved a container C intoposition to be sealed. Retraction of the piston rod 280 causes thehooked ends of arms 286 to engage the associated carrier 253 thuscausing the carriage 266 to move with the processing conveyor 100 duringthe sealing operation from the position shown in FIG. 11 to the positionshown in FIG. 12.

The sealing ram 274 includes a cylinder 290 which is pivotally connectedto the sub-frame 270 of carriage 266 and also includes a piston rod 292which is connected to a triangular plate 294 (FIGS. 9 and The plate 294is pivotally connected to one end of two spaced levers 296 pivoted onthe sub-frame 270 by pins 298. Each lever 296 operates one of the twosealing heads 23 which heads are identical and therefore only one headwill be described in detail.

The other end of each lever 296 is connected to a pin 300 which ispivotally connected to the upper end of two sets of links 302 and 304.The links 302 are pivotally connected to arms 306 that are pivoted abouta pin 308 connected to the sub-frame 270 and have a first sealing bar309 rigidly secured thereto. Similarly the links 304 are pivotallyconnected to a pair of arms 310 that are pivoted about the pin 308 andhave a second sealing bar 311 rigidly secured therewith. As is wellknown in the art, at least one of the sealing bars has a generallysemicylindrical surface which is heated by an electrical coil EC (FIG.4) to raise the temperature thereof to the bonding temperature, i.e.,between about 250 to 300 F., while the other sealing bar has a hardrubber surface and acts as a pressure resisting member. However, bothsealing bars are preferably heated by electrical coils EC, and are heldtogether with a pressure which applies a force to the container beingsealed above about 100 p.s.i. and preferably about 250 p.s.i.

The carriage return ram 276 is actuated after the sealing operation hasbeen completed to return the carriage from its extended position shownin FIG. 12 to its retracted position shown in FIG. 11. The ram 276includes a cylinder 312 which is secured to the carriage 266 and apiston rod 314 which is secured to the stationary frame 258.

As diagrammatically illustrated in FIG. 14, the sealing apparatus of thesecond embodiment of the invention is controlled by pneumatic andelectrical circuit 320. The circuit 320 includes a four-way solenoidvalve 322 which is shiftable from the illustrated parallel passageposition to a cross passage position upon energization of solenoid 324.Prior to movement of the container into position to be sealed, the partsof the apparatus 22 are positioned as shown in FIGS. 11 and 14 and thesolenoid 324 is deenergized. When in this position air from a highpressure source is directed into the four-way valve 322 through apressure regulator PR and high pressure conduit HP and air is ventedfrom the valve through conduit V. The pressure regulator PR is of thewell known adjustable type which may be adjusted so as to provide asealing pressure above p.s.i., preferably about 250 p.s.i. The highpressure air flows through a parallel passage in the valve 322, througha conduit 326 and speed control valve SC to the cylinder 278 of theindexing ram 272. High pressure air is directed into the cylinder 290 ofthe sealing ram 274 through conduits 328 and 330. A conduit 332 having asolenoid valve 334 therein connects the conduit 328 to a cylinder 312 ofthe carriage return ram 276 to direct high pressure air therein when thesolenoid 336 of valve 334 is energized as illustrated. At this time, airis vented from the cylinder 278 of the indexing ram 272 through aconduit 340 which communicates with the vent conduit V through aparallel passage in the valve 322. The cylinder 290 of the sealing ram274 is vented through a conduit 342 which is connected between thecylinder 290 and the conduit 340 and has a speed control valve SCtherein. The cylinder 312 of the carriage return ram 276 is ventedthrough a conduit 344 connected between the cylinder 312 and the conduit342 and has a solenoid valve 346 therein which includes a solenoid 348.

The solenoid valves 334 and 346 each include a core having a straightpassage therein which permits fluid to flow through the conduits 332 and344, respectively, when the valves are energized. The cores of valves334 and 346 also include slanted passages which when the valves aredeenergized serve to bleed fluid from both sides of the cylinder 312 ofram 276 and to prevent high pressure air from entering either side ofthe cylinder 312.

As illustrated in FIG. 14, both solenoid valves 334 and 346 areenergized in response to the closing of a limit switch LS1 which isconnected in series between main lines L1 and L2 with solenoids 336 and348 of solenoid valves 334 and 346. The switch LS1 is closed in responseto movement of the holding arms 286 to their inactive upper position asillustrated in FIG. 11, and is opened when the arms move downwardly intoengagement with the processing conveyor 100. The solenoid 324 of thefour-way valve 322 is energized in response to one of the doublecarriers 253 contacting an actuating element 348 of a limit switch LS2thereby momentarily closing the switch. Closing of switch LS2 energizesthe relay R of a timer or time delay relay through closed timer contactTC. Energization of timer relay R closes relay contact R-l whichestablishes a holding circuit across switch LS2, and also closes relaycontact R-2 which closes a circuit to the solenoid 324 of the four-wayvalve 322 thereby shifting the valve to the crosspassage position.

In the operation of the sealing apparatus 22 of the second embodiment ofthe invention, filled but unsealed flexible containers C are manuallyplaced in the double carriers 253 (F IO. 13) and are clamped in positionby the clips 255 and 256. The continuously driven conveyor 100 thenadvances the containers through the preheating liquid in the inlethydrostatic leg 88 and through the sterilizing medium in the sterilizingchamber 76. Prior to leaving the sterilizing chamber 76, the containersare moved into and through the sealing station SS.

As the pair of flexible containers C move into position to be sealed,their supporting carrier 253 engages and closes limit switch LS2 therebyenergizing the relay R of the timer, closing relay contact R-1 and R-2.Closing of relay contacts R-1 and R-2 causes the energization ofsolenoid 324 of the four-way valve 322. Energization of thesolenoidvalve 322 moves the valve core to the cross passage position. Highpressure fluid then flows directly into the cylinder 278 of the indexingram 272 through conduit 340 thereby rapidly moving the hooking arms 286into engagement with the carriers 253 causing the carriage 266 to movewith the conveyor 100. Downward movement of the arms 286 causes theswitch LS1 to open thereby simultaneously deenergizing both solenoidvalves 334 and 346 causing the slanted passages to register with theconduits 332 and 344 thus bleeding air from both ends of the carriagereturn cylinder 312 and preventing high pressure fluid from flowing intothe cylinder 312. High pressure fluid also flows into the cylinder 290of the sealing ram 274 but its flow is restricted slightly by the speedcontrol SC thereby assuring that the carriage 266 is locked in sealingposition to the conveyor 100 before the sealing jaws engage thecontainers.

The valves 322, 334 and 346 remain in the positions describedimmediately above until the dwell period set on the timer, i.e., between2 to 6 seconds, elapses at which time the timer switch TC momentarilyopens to deenergize timer relay R thereby opening contacts R-1 and R-2and deenergizing solenoid 324 of four-way valve 322 returning the valveto the parallel passage position shown in FIG. 14.

High pressure fluid then flows through conduits 326, 328 and 330 to thecylinder 290 of sealing ram 274 thereby rapidly opening the sealing barsreleasing the sealed containers. High pressure fluid also flows throughconduit 326 and speed control valve SC into the cylinder 278 of indexingram 272. The speed control valve SC is set to reduce the rate of flow offluid into the cylinder 278 to assure that the sealing jaws will releasethe container before the arms 286 are disengaged from the conveyor 100.When the arms 286 move to their uppermost position, the switch LS1closes thereby energizing both solenoid valves 334 and 346. Highpressure fluid then flows through valve 334 and conduit 332 into thecylinder 312 of carriage return ram 276 thereby moving the carriage toits retracted position as illustrated in FIG. 11 thus completing a cycleofoperation of the sealing apparatus.

The sterilized and sealed containers are then conveyed out of the cookerthrough the cooling water in hydrostatic outlet water leg 92 to cool thecontents of the containers, and the containers are subsequently removedfrom their carriers.

In the above description of the apparatus 22 of the second embodiment ofthe invention it will be understood that the speed control valves SC areidentical to the speed control valves SC of the first embodiment of theinvention and that these valves SC may be adjusted to provide a desiredrate of fluid flow therethrough.

It will also be understood that the temperature of the heat treatmentmedium in the first embodiment of the invention may be slightly below212 F. if it is desired to pasteurize rather than sterilize the contentsof the containers.

From the foregoing description it is apparent that the sealing methodand apparatus of the present invention contemplates sealing flexiblecontainers while heated at a temperature equal to or substantially equalto the sterilizing temperature by subjecting the containers to therelatively low temperature of about 250 to 300 F., at a pressure aboveabout 100 p.s.i. and preferably about 250 psi, for a long dwell periodof between about 2 to 6 seconds and preferably about 4 seconds.

Although the best mode contemplated for carrying out the presentinvention has been herein shown and described, it will be apparent thatmodification and variation may be made without departing from what isregarded to be the subject matter of the invention.

1 claim:

1. An apparatus for sealing flexible containers having walls defined byadjacent layers of heat sealable thermoplastic material and having anunsealed mouth, comprising a housing; means for supporting and movingthe containers along a predetermined path and through said housing; asealing head adjacent said path; said sealing head including a pair ofsealing bars, means for heating at least one of said sealing bars to atemperature within the range of about 250 to 300 F., power means formoving said bars between an inactive position spaced from each other andan active position clamping the portion of a container to be sealedtherebetween with a pressure of above about 100 psi, and control meansfor maintaining the sealing bars in said active position for a period ofbetween about 2 to 6 seconds, said housing including a sterilizingchamber having a sterilizing medium therein maintained at a sterilizingtemperature, and said sealing head being disposed within saidsterilizing chamber.

2. An apparatus for sealing flexible containers according to claim 1wherein said sterilizing temperature is about 212 F.

3. An apparatus for sealing flexible containers according to claim 1wherein said sterilizing temperature is about 250 F.

4. An apparatus for sealing flexible containers having walls defined byadjacent layers of heat sealable thermoplastic material and having anunsealed mouth, comprising a continuously driven conveyor for supportingand moving the containers along a predetermined path, a sealing headmounted for pivotal movement about a shaft defining a pivot axis spacedfrom said path, said sealing head including a pair of sealing bars,means for heating said bars to a bonding temperature, first poweractuated means carried by said sealing head for connecting said head tosaid conveyor during the sealing operation and for causing a portion ofthe conveyor that is connected to said sealing head to move in anarcuate path about said axis during the sealing operation, and secondpower means connected to said sealing bars for moving said bars betweenan inactive position spaced from each other and an active positionclamping the portion of a container to be sealed therebetween under apressure sufficient to seal the container, and control means formaintaining the sealing bars in said active position for a period ofbetween about 2 to 6 seconds.

5. An apparatus for sealing flexible containers according to claim 4wherein said connecting means is in the form of a finger which is urgeddownwardly into engagement with said conveyor when a container has movedinto position to be sealed, said finger being effective to push saidconveyor downwardly out of its normal path of travel so that saidcontacted portion of said conveyor will move through an arcuate pathabout said axis during the sealing operation.

6. An apparatus for sealing flexible containers according to claim 1wherein said means for supporting and moving the containers is acontinuously driven conveyor, wherein means are provided to connect thesealing head with the conveyor for movement therewith when the sealingbars are in their active sealing positions, and wherein said sealinghead is mounted for pivotal movement about a shaft defining an axisspaced a distance greater than the length of the container from saidpath, and wherein power actuated means is carried by said sealing headfor connecting said head to said conveyor during the sealing operationfor pivotal movement about said axis.

7. An apparatus for sealing flexible containers having walls defined byadjacent layers of heat scalable thermoplastic material and having anunsealed mouth, comprising a housing; means for supporting and movingthe containers along a predetermined path and through said housing; asealing head adjacent said path; said sealing head including a pair ofsealing bars, means for heating at least one of said sealing bars to atemperature within the range of about 250 to 300 F., power means formoving said bars between an inactive position spaced from each other andan active position clamping the portion of a container to be sealedtherebetween with a pressure of about p.s.i., and control means formaintaining the sealing bar in said active position for a period ofbetween about 2 to 6 seconds, said means for supporting and moving thecontainers being a continuously driven conveyor, means provided toconnect the sealing head with the conveyor for movement therewith whenthe sealing bars are in their active sealing position; said sealing headincluding a pair of spaced downwardly extending arms secured to saidshaft, a pivot shaft secured to the lower portions of said arms, a firstpair of levers pivotally connected to said pivot shaft, one of saidsealing bars secured to the lower end of said first pair of levers, asecond pair of levers pivotally connected to said pivot shaft, saidother sealing bar secured to the lower ends of said second pair oflevers, a cam plate supported and guided by said arms for moving in apath parallel thereto and having first and second symmetrical slotstherein, a first shaft connected to the other ends of said first pair oflevers and passing through said first slot, and a second shaft connectedto the other ends of said second pair of levers and passing through saidsecond slot, said power means connected between said first and saidsecond shafts for moving said sealing bars between said first and saidsecond positions.

8. An apparatus for sealing flexible containers having walls defined byadjacent layers of heat sealable thermoplastic material and having anunsealed mouth, comprising a housing; means for supporting and movingthe containers along a predetermined path and through said housing; asealing head adjacent said path; said sealing head including a pair ofsealing bars, means for heating at least one of said sealing bars to atemperature within the range of about 250 to 300 F power means formoving said bars between an inactive position spaced from each other andan active position clamping the portion of a container to be sealedtherebetween with a pressure of about 100 p.s.i., and control means formaintaining the sealing bars in said active position for a period ofbetween about 2 to 6 seconds; said means for supporting and moving thecontainers being a continuously driven conveyor; and additionallycomprising a carriage, said sealing head being mounted on said carriage,hooking means carried by said carriage for connecting the carriage tothe conveyor for movement therewith when the sealing bars are in theiractive sealing positions, first power means for operating said hookingmeans, second power means carried by said carriage and connected to saidsealing bars for moving said sealing bars between the active and theinactive positions, third power means connected between said carriageand said housing for moving the carriage in a direction opposite to thedirection of movement of the conveyor after a container has been sealedand the sealing bars have been moved to their inactive positions, andcontrol means for controlling the actuation of said power means in timedrelation with the movement of said conveyor. v

9. An apparatus for sealing flexible containers according to claim 8wherein said control means includes means responsive to the release ofthe hooking means from said conveyor for actuating said third powermeans for returning the carriage to its starting position.

10. An apparatus for sealing flexible containers according to claim 8wherein said housing includes a sterilizing chamber having a sterilizingmedium therein maintained at a sterilizing temperature, and wherein saidcarriage and sealing head are disposed in said sterilizing chamber.

11. An apparatus for sealing flexible containers according to claim 10wherein one of the sealing jaws has a convex container contactingsurface which serves to extrude contaminated material out of the sealarea before the thermoplastic material becomes tacky.

1. An apparatus for sealing flexible containers having walls defined byadjacent layers of heat sealable thermoplastic material and having anunsealed mouth, comprising a housing; means for supporting and movingthe containers along a predetermined path and through said housing; asealing head adjacent said path; said sealing head including a pair ofsealing bars, means for heating at least one of said sealing bars to atemperature within the range of about 250* to 300* F., power means formoving said bars between an inactive position spaced from each other andan active position clamping the portion of a container to be sealedtherebetween with a pressure of above about 100 p.s.i., and controlmeans for maintaining the sealing bars in said active position for aperiod of between about 2 to 6 seconds, said housing including asterilizing chamber having a sterilizing medium therein maintained at asterilizing temperature, and said sealing head being disposed withinsaid sterilizing chamber.
 2. An apparatus for sealing flexiblecontainers according to claim 1 wherein said sterilizing temperature isabout 212* F.
 3. An apparatus for sealing flexible containers accordingto claim 1 wherein said sterilizing temperature is about 250* F.
 4. Anapparatus for sealing flexible containers having walls defined byadjacent layers of heat sealable thermoplastic material and having anunsealed mouth, comprising a continuously driven conveyor for supportingand moving the containers along a predetermined path, a sealing headmounted for pivotal movement about a shaft defining a pivot axis spacedfrom said path, said sealing head including a pair of sealing bars,means for heating said bars to a bonding temperature, first poweractuated means carried by said sealing head for connecting said head tosaid conveyor during the sealing operation and for causing a portion ofthe conveyor that is connected to said sealing head to move in anarcuate path about said axis during the sealing operation, and secondpower means connected to said sealing bars for moving said bars betweenan inactive position spaced from each other and an active positionclamping the portion of a container to be sealed therebetween under apressure sufficient to seal the container, and control means formaintaining the sealing bars in said active position for a period ofbetween about 2 to 6 seconds.
 5. An apparatus for sealing flexiblecontainers according to claim 4 wherein said connecting means is in theform of a finger which is urged downwardly into engagement with saidconveyor when a container has moved into position to be sealed, saidfinger being effective to push said conveyor downwardly out of itsnormal path of travel so that said contacted portion of said conveyorwill move through an arcuate path about said axis during the sealingoperation.
 6. An apparatus for sealing flexible containers according toclaim 1 wherein said means for supporting and moving the containers is acontinuously driven conveyor, wherein means are provided to connect thesealing head with the conveyor for movement therewith when the sealingbars are in their active sealing positions, and wherein said sealinghead is mounted for pivotal movement about a shaft defining an axisspaced a distance greater than the length of the container from saidpath, and wherein power actuated means is carried by said sealing headfor connecting said head to said conveyor during the sealing operationfor pivotal movement about said axis.
 7. An apparatus for sealingflexible containers having walls defined by adjacent layers of heatsealable thermoplastic material and having an unsealed mouth, comprisinga housing; means for supporting and moving the containers along apredetermined path and through said housing; a sealing head adjacentsaid path; said sealing head including a pair of sealing bars, means forheating at least one of said sealing bars to a temperature within therange of about 250* to 300* F., power means for moving said bars betweenan inactive position spaced from each other and an active positionclamping the portion of a container to be sealed therebetween with apressure of about 100 p.s.i., and control means for maintaining thesealing bar in said active position for a period of between about 2 to 6seconds, said means for supporting and moving the containers being acontinuously driven conveyor, means provided to connect the sealing headwith the conveyor for movement therewith when the sealing bars are intheir active sealing position; said sealing head including a pair ofspaced downwardly extending arms secured to said shaft, a pivot shaftsecured to the lower portions of said arms, a first pair of leverspivotally connected to said pivot shaft, one of said sealing barssecured to the lower end of said first pair of levers, a second pair oflevers pivotally connected to said pivot shaft, said other sealing barsecured to the lower ends of said second pair of levers, a cam platesupported and guided by said arms for moving in a path parallel theretoand having first and second symmetrical slots therein, a first shafTconnected to the other ends of said first pair of levers and passingthrough said first slot, and a second shaft connected to the other endsof said second pair of levers and passing through said second slot, saidpower means connected between said first and said second shafts formoving said sealing bars between said first and said second positions.8. An apparatus for sealing flexible containers having walls defined byadjacent layers of heat sealable thermoplastic material and having anunsealed mouth, comprising a housing; means for supporting and movingthe containers along a predetermined path and through said housing; asealing head adjacent said path; said sealing head including a pair ofsealing bars, means for heating at least one of said sealing bars to atemperature within the range of about 250* to 300* F., power means formoving said bars between an inactive position spaced from each other andan active position clamping the portion of a container to be sealedtherebetween with a pressure of about 100 p.s.i., and control means formaintaining the sealing bars in said active position for a period ofbetween about 2 to 6 seconds; said means for supporting and moving thecontainers being a continuously driven conveyor; and additionallycomprising a carriage, said sealing head being mounted on said carriage,hooking means carried by said carriage for connecting the carriage tothe conveyor for movement therewith when the sealing bars are in theiractive sealing positions, first power means for operating said hookingmeans, second power means carried by said carriage and connected to saidsealing bars for moving said sealing bars between the active and theinactive positions, third power means connected between said carriageand said housing for moving the carriage in a direction opposite to thedirection of movement of the conveyor after a container has been sealedand the sealing bars have been moved to their inactive positions, andcontrol means for controlling the actuation of said power means in timedrelation with the movement of said conveyor.
 9. An apparatus for sealingflexible containers according to claim 8 wherein said control meansincludes means responsive to the release of the hooking means from saidconveyor for actuating said third power means for returning the carriageto its starting position.
 10. An apparatus for sealing flexiblecontainers according to claim 8 wherein said housing includes asterilizing chamber having a sterilizing medium therein maintained at asterilizing temperature, and wherein said carriage and sealing head aredisposed in said sterilizing chamber.
 11. An apparatus for sealingflexible containers according to claim 10 wherein one of the sealingjaws has a convex container contacting surface which serves to extrudecontaminated material out of the seal area before the thermoplasticmaterial becomes tacky.